Smysl bioremediace = využít přirozené biodegradační pochody s cílem vyčistit kontaminované lokality. - systém, kdy se do půdy navrací ekologická funkce, kterou plní mikroorganismy Pokud mikroorganismy selhaly: • není žádná skupina, která by byla schopna mineralizovat či detoxifikovat daný kontaminant • rychlost vstupu kontaminantu je větší než rychlost dekompozice • chemické, fyzikální, či biologické limitace dekompozitorů • polutant či koncentrace, které jsou toxické pro dekompozitory • fyzikální či chemické faktory, které zabraňují kontaktu dekompozitorů a polutantů • dekontaminace vede k podmínkám inhibující další procesy .'■ .'■ .'■ .'■ .'■ .'■ bioremediace = mnohdy více technika než biologie či ekotoxikologie = management půdních fyzikálních, chemických, biologických a dalších faktorů tak, aby se výše uvedené body minimalizovaly a detoxifikační schopnost mikroorganismů byla co nejvyšší - cílem tedy je detoxifikace, immobilizace, či mineralizace žádané látky (nej častej i organických polutantů a sloučenin) ___________^ přirozená (bez managementu) in situ -====:^^^^~~~~~. --------► řízená ex situ Schéma bioremediace ■ ■ ■ ■ ■ ■; - ' Faktory prostředí: pH, Eh, T, vlhkost, - živiny ■ j BIOREMEDIACE \\ ■ ■ ■; y *tŕ y ^ y ^ y vv° y / & y í ^ y y y x \ ■ y \ x \ \ x X ' \ X Y >v X 2 Table 15-1 Comparison of In situ and Ex situ Strategies for Engineered BioremediatK 3n Systems In Situ Ex Situ Location In the landscape In a controlled bioreactor Requirements Engineer the landscape to resemble a Move contaminants from landscape to laboratory flask on-site bioreactors Characteristics Relatively poor control of biodegradation process Greater control Obstacles Complexities of landscape that may Complexities of landscape partially prevent success overcome Pollutant mixtures Pollutant mixtures Unknown site histories Unknown site histories Mass balances uncertain Decent bioreactor mass balances Biotic versus abiotic processes Biotic processes defined in bioreactor Incompatibility of site characteristics Incompatibility of site characteristics and microbiological processes and microbiological processes Production of pollutants by Production of pollutants by microorganisms microorganisms 1 How clean is clean? How clean is clean? Nezbytné je zabezpečit optimální podmínky biodegradace Přidávání kyslíku a jiných plynů: - bioventing je technika dodávky kyslíku přímo in situ do nesaturované zóny - "air sparging" - tlakové vhánění kyslíku do saturační zóny - kromě kyslíku se často dodává methan (zejména při degradacích chlorovaných látek) Dodávka živin: - hlavně přídavky dusíku a fosforu - cíl: optimalizace poměru C:N:P na hodnotu cca 100:10:1 Stimulace anaerobních degradací: - dodávka alternativních TEA (terminal electron acceptor) - dusičnany, sírany, Fe3+, C02 - anaerobní degradace je sice pomalejší, ale dokáže "si poradit" s jinými polutanty než aerobní degradace (např. silně chlorované látky) Dodávka surfaktantů: - sniží povrchové napětí a zvýší biodostupnost kontaminantů Dodávka mikroorganismů či DNA: - introdukované organismy - bioaugmentace - genetické inženýrství, uměle vytvořené mikroorganismy schopné vysoce efektivních biodegradací Problémy: - neschopné dlouho přežít v reálném ekosystému - vážou se na půdní komplexy a tím jsou méně aktivní 4 Bioremediace a biodegradace TABLE 16.3 Current Status of Bioremediation Freqiipnry of Status of Chemical class occurrence bioremediation Evidence of future success Limitations Hydrocarbons and derivatives Choline, fuel oil Very frequent Kstablished Forms nonaqueous phase liquid !JAHs Common Kinerging Aerobieally biodegradable under a narrow range of conditions Sorbs strongly to subsurface soilds Creosole Infrequenl Kmerging Readily biodegradable under aerobic.: conditions Sorbs strongly to subsurface soilds; Alcohols, ketones, esters Common Established forms nonaqueous phase liquid h t hers (common emerging Biodegradable under a narrow range of conditions using aerobic or nitrate-reducing microbes Halogenaled aliphatic? Highly chlorinated Very frequent Emerging Cometabolized by anaerobic microbes; cometaboliwd by aerobes in special Forms nonaqueous phase liquid Less chlorinated Very frequent F merging Aerobically biodegradable under a narrow range of conditions; cometabolized by anaerobic microbes Forms nonaqueous phase liquid Halogenated aromatics Highly chlorinated Common Kmerging Aerobicaily biodegradable under ;i narrow range of conditions; cometabolized by anaerobic microbes Sorbs strongly to subsurface solids; forms nonaqueous phase either liquid or solid Less ehlorinated Common Emerging Readily biodegradable under aerobic conditions Forms nonaqueous phase either liquid or solid Polycholorinated biphenyls Highly chlorina Led Infrequent Rmerging Cometabolized by anaerobic microbes Sorbs strongly to subsurface solids Less chlorinated Infrequent RllUTgillg Aerobic Íly biodegradable under a narrow range of conditions Sorbs strongly to subsurface solids Nitroaroamatics Common Emerging Aerobicaily biodegradable; converted to innocuous volatile organic acids under anaerobic conditions Metals (Cr, Cu, XL Pb, 1 [g, Cd, Common Possible (see Sol ubi iity and reactivity can be changed by a variety of microbial processes Availability highly variable and 7nr etc) Chapter 17) controlled by solution and solid-phase chemistry Adapted Írom National Resei treh Council (1993) 5 83 Bioremediace a biode^ ;radace , Table 15-2 An Overview of Relationships between Chemicals, Their Properties, and Bioremediation Prospects Biodegradability5 Frequency of Partitioning Prospects for Chemical Classes" Hydrocarbons (A, N, AN) Mobility' Occurrenced Reactions' Bioremediationf BTEX Al, N2,AN2 H F M Es Low MW, gasoline, #2 fuel oil Al, N3, AN2 M F M Es High MW. oil, PAH A2, N4, AN4 L C S Em Creosote Al, N2, AN4 L I S Em Oxygenated hydrocarbons Low MW alcohols, ketones, esters, ethers Al, N5, AN3 H C W Es Halogenated aliphatics Highly chlorinated A4, A3, N5, AN2 M F M Em Less chlorinated A2, A3, N5, AN2 H F M Em Halogenated aromatics Highly chlorinated A4, A2, N5, AN2 L C S Em Less chlorinated A2, A3, N2, AN2 M C M Em PCBs Highly chlorinated A4, N5, AN2 L I S Em Less chlorinated A2, Al, N5, AN4 L I S Em Nitroaromatics A2, N5, AN2 M C M Em "BTEX = benzene, toluene, ethylbenzene , xylenes; MW = molecular weight; PAH = polycyclic aromatic hydrocarbon; PCBs = - polychlorinated biphenyl s. bThe three alphanumeric entries for each compound provi de a biodegradability rating (1-5) under aerobic (A), nitrate-reducing (N), and other anaerobic (AN) conditions. 1 = readily mineralizabie as growth substrate; 2 = biodegradable under narrow range ( af conditions; 3 = metabolized partially when second substrate is present (co-metabolized); 4 = resistant; 5 = insufficient informatior i. CH = highly mobile; M = moderately mobile; L = least mobile. ''Based on survey of groundwater contaminants. F = very frequent; C = common; I = Infrequent. eS = strong sorptive characteristics; M = moderate characteristics; W = weak characteristics. fEs = established; Em = emerging. 6 a) In situ bioremediation in the vadose zone and groundwater. Nutrients and oxygen are pumped into the contaminated area to promote in situ 'processes. This figure also shows ex situ treatment. Ex situ treatment is for water pumped to the surface and uses an aboveground bioreactpr, as shown, or other methods, e.g. air stripping, activated carbon, off-water separation, or oxidation. An injection well returns treated water to the aquifer. b) Bioventing and biofiltration in the vadose zone. Air drawn through the contaminated site (bioventing) stimulates in situ aerobic degradation. Volatile contaminants removed with the air are treated in a biofilter,by adsorption on activated carbon, or by combustion. c) Bioremediation in the groundwater by air sparging. Air pumped into the contaminated site stimulates aerobic degradation in the saturated zone. Volatile contaminants brought to the surface are treated by biofiltration, activated carbon, or combustion. From Pollution Science ©1996, Academic Press, San Diego, CA.) Nutrient Tank (N&P) Oxygen Source rc Vacuum Injection Gallery iir uumunuunii Vadose v Groundwater Option 1 Option 2 mm Adsorption on Activated Carbon Option 3 Combustion 3T-- —* Air Status Uncorttammated [__J Contaminated Bi Groundwater Option 1 B iof titration Option 2 | Option 3 Adsorption on Activated Carbon II ombustion i n ^ «»J n Vadose Zone Weil/"* Flow f | Pi * Contaminated Groundwater Air Status Uncontaminated t~3 Contaminated M liodegradace Figure 14.4 Bioremediation of PCB-contaminated river sediments. (A) Placement of steel caissons into ^ZÍÍÍľľttraCÍng Sh0WÍng fU" "***<* conlamlnatlnfl^B SS^i J) Nutrients added to sealed caissons lead to creation of anaerobic conditions- anaerobic dehalogenation converts higher-molecular-weight congeners to ones with fewer chtor nes Chromatograph, tracing shows disappearance of higher-molecular-weight congenľr with 4-6 chlonnes and increased concentrations of lower-molecular-weight PCBs wi h 2-3 chlonnes. (C) Forced aeration and stirring create aerobic conditions; biodegradá ion af lower-molecular-weight congeners leads to cleaner sediments Dloae9radat,on Kovy - jednoprvkové polutanty - jiný princip: - není biodegradace, proto 1) immobilizace kovu in situ (zabrání mobilitě a biodostupnosti) a 2) odstranění kovů Microbial remediation of metal-contaminated soil in-situ/ex-situ metal removal -metal oxidation -metal leaching e.g., acid production, chelation, _surfactant_production, volatilization i Increased metal solubility and enhanced recovery 1 Treated soil available for re-use In-situ metal immobilization -microbial binding e.g. EPS production, metal reduction Decreased metal solubility and decreased toxicity i Treated soil cannot be disturbed; potential risk of metal exposure' remains; requires regular monitoring FIGURE 17.14 Microbial metal remediation in metal-contaminated soils relies on either metal removal or more commonly, metal nnmobilrzahon. Metal removal is idea, because following treatment th scľl ľľva\ b e for reuse. In metal nnmoMHzaüoa soil reuse is limited because of the OM^J^öl^^^^ Microbial oxidation e.g. volatilization Treated water available for re-use Microbiological remediation of metal-contaminated water In-situ/ex-situ metal removal \ Microbial binding e.g. EPS Recovery of metals bound by microorganisms I Treated water available for re-use Microbial reduction e.g. precipitation i Recovery of metal containing precipitate via sedimentation or filtration I Treated water available for re-use FIGURE 17.15 Microbial metal remediation approaches for metal-contaminated waters. In each method, the treated water is safe to release into the environment. Both metals and microorganisms can easily be recovered during treatment for proper disposal. 10 Canal to channel Outfall water flow FIGURE 17.16 Schematic demonstrating how microbial biofilms are used in removing metals from contaminated wastestreams. The biofilm located on the rotating drum accumulates metals as the water passes through the drum. The treated water can be safely released. The bio film may either be viable or nonviable. When viable, the biofilm rarely needs to be replaced; however, non-living biorilms need to be replaced periodically for their metal removal efficiency will decrease with time. 11